Anguita-Maeso Manuel, Navas-Cortés Juan A, Landa Blanca B
Department of Crop Protection, Institute for Sustainable Agriculture, Spanish National Research Council (CSIC), 14004 Córdoba, Spain.
Plants (Basel). 2023 Feb 17;12(4):912. doi: 10.3390/plants12040912.
Vascular pathogens are the causal agents of some of the most devastating plant diseases in the world, which can cause, under specific conditions, the destruction of entire crops. These plant pathogens activate a range of physiological and immune reactions in the host plant following infection, which may trigger the proliferation of a specific microbiome to combat them by, among others, inhibiting their growth and/or competing for space. Nowadays, it has been demonstrated that the plant microbiome can be modified by transplanting specific members of the microbiome, with exciting results for the control of plant diseases. However, its practical application in agriculture for the control of vascular plant pathogens is hampered by the limited knowledge of the plant endosphere, and, in particular, of the xylem niche. In this review, we present a comprehensive overview of how research on the plant microbiome has evolved during the last decades to unravel the factors and complex interactions that affect the associated microbial communities and their surrounding environment, focusing on the microbial communities inhabiting the xylem vessels of olive trees (Olea europaea subsp. europaea), the most ancient and important woody crop in the Mediterranean Basin. For that purpose, we have highlighted the role of xylem composition and its associated microorganisms in plants by describing the methodological approaches explored to study xylem microbiota, starting from the methods used to extract xylem microbial communities to their assessment by culture-dependent and next-generation sequencing approaches. Additionally, we have categorized some of the key biotic and abiotic factors, such as the host plant niche and genotype, the environment and the infection with vascular pathogens, that can be potential determinants to critically affect olive physiology and health status in a holobiont context (host and its associated organisms). Finally, we have outlined future directions and challenges for xylem microbiome studies based on the recent advances in molecular biology, focusing on metagenomics and culturomics, and bioinformatics network analysis. A better understanding of the xylem olive microbiome will contribute to facilitate the exploration and selection of specific keystone microorganisms that can live in close association with olives under a range of environmental/agronomic conditions. These microorganisms could be ideal targets for the design of microbial consortia that can be applied by endotherapy treatments to prevent or control diseases caused by vascular pathogens or modify the physiology and growth of olive trees.
维管病原体是世界上一些最具毁灭性的植物病害的致病因子，在特定条件下，它们可导致整片作物被毁。这些植物病原体在感染宿主植物后会激活一系列生理和免疫反应，这可能会引发特定微生物群落的增殖，通过抑制病原体生长和/或争夺空间等方式来对抗它们。如今，已经证明通过移植微生物群落的特定成员可以改变植物微生物群，这在植物病害防治方面取得了令人兴奋的成果。然而，由于对植物内圈，特别是木质部生态位的了解有限，其在农业中用于防治维管植物病原体的实际应用受到了阻碍。在本综述中，我们全面概述了过去几十年间植物微生物群研究是如何发展的，以揭示影响相关微生物群落及其周围环境的因素和复杂相互作用，重点关注居住在地中海盆地最古老且最重要的木本作物橄榄树（油橄榄亚种）木质部导管中的微生物群落。为此，我们通过描述为研究木质部微生物群而探索的方法，突出了木质部组成及其相关微生物在植物中的作用，从用于提取木质部微生物群落的方法到通过依赖培养和下一代测序方法进行的评估。此外，我们对一些关键的生物和非生物因素进行了分类，如宿主植物生态位和基因型、环境以及维管病原体感染，这些因素在全生物背景（宿主及其相关生物）下可能是严重影响橄榄生理和健康状况的潜在决定因素。最后，我们根据分子生物学的最新进展，概述了木质部微生物群研究的未来方向和挑战，重点是宏基因组学、培养组学和生物信息学网络分析。更好地了解橄榄木质部微生物群将有助于促进对特定关键微生物的探索和选择，这些微生物能够在一系列环境/农艺条件下与橄榄紧密共生。这些微生物可能是设计微生物联合体的理想目标，可通过内治疗法来预防或控制维管病原体引起的疾病，或改变橄榄树的生理和生长。
